The present invention relates to a method for producing a fuel tank provided with (at least partly) internal accessories and in particular a component for putting the inside and outside of said tank into fluid communication.
Fuel systems on board vehicles of various types generally comprise devices which provide ventilation of hydrocarbons contained in the tank. They may also comprise devices for supplying the engine with fuel. Such devices form a link between the components contained in the tank (valves, fuel pump, etc.) and components positioned outside this (canister, filling pipe, etc.). The passage through the wall of the tank must be made taking into account the leakproof requirements laid down by current environmental standards (LEV II, PZEV for example). To this end, the reduction in the number and size of openings in the wall of the tank constitutes a favourable factor in the reduction of evaporation losses. However, this makes it more difficult to insert and position components inside the tank.
Moreover, the tank is generally fitted with circuits (for example for ventilation, fuel supply) comprising pipes, valves, small pipes etc. positioned inside the tank and, as the case may be, connected to components situated outside the tank. Now, when fluid communication is made between the inside and outside of the tank through the wall, it is possible, according to the position of the opening in the wall (for example at the location of a plate), that siphons are created in the pipes. In the case of ventilation circuits, these constitute a disadvantage, since the accumulation of liquid conveyed by vapours can lead to a malfunction of the ventilation system. In addition, in the case of fuel supply lines, it is possible that the location of the plate involves a detour or an unnecessary length of said pipe.
Finally, the tank generally includes other accessories such as an anti-wave (and an associated anti-noise) baffle or baffles, a device for separating liquid from vapour, a gauge or gauges for measuring the fuel level, a reserve tank etc. The object of the latter is to prevent failure of the pump to prime in the case where the vehicle runs out of fuel or when it is parked for a long time on a slope for example. It is generally provided with a valve (“first fill valve”) making it possible to fill it when the tank is first filled and/or after running out of fuel, and its size is generally limited by the size of the orifice to be made in the tank in order to be able to introduce it therein.
All these internal accessories (more exactly at least partly internal accessories) are generally placed/attached inside the tank after this is moulded, by separate operations that take time and labour and are therefore costly. Moreover, as previously mentioned, with a view to reducing the size and number of orifices through the wall for introducing said accessories, an attempt is often made to group these together and, on account of this, their location is not optimal (that is to say the performance of said accessory is not optimized).
Application EP 1110697 in the name of the Applicant discloses a method for moulding a fuel tank using a parison in several parts so as to be able to insert the accessories into the tank at the same time as it is moulded. With a view to reducing the number of components to be introduced and fastened inside the tank, this document recommends the use of pre-assembled structures, which solves the problem of the number of openings and of the overall duration of the moulding cycle, but does not always solve the problem of an optimized location for the various accessories. The object of the invention is consequently to provide a method which enables this problem to be solved and this by virtue of the use of a single support (called a “core”) on which the accessories are positioned in an ideal layout and which makes it possible to fasten said accessories at their ideal location in the tank in a single step. In particular, in a variant, the method according to the invention makes it possible to produce a fuel tank made of plastic with fluid communication between the inside and outside of said tank, through an opening with reduced dimensions, the location of which may be freely chosen so as to prevent the creation of siphons and/or detours of the lines and this by means of a method involving a minimum number of steps.